This investigation was conducted at the Experimental Farm Faculty of Agriculture, Al-Azhar
Univ., Assiut during the two successive seasons of 2018 and 2019 to determine the influence of compost as organic
fertilization and foliar Spray with stimulant substance namely (amino acids [tryptophan + methionine +
phenylalanine], silicon and seaweeds extract), as well as their interactions on plant growth traits, sepals. yield /
plant and fed. and active ingredients of roselle (Hibiscus sabdariffa, L.) C.V. "Sabahia 17" dark line plants.
Compost was applied at 0, 8, 16 and 24 m³/ fed., and spraying the plants with the three examined stimulant
substances as follows: control (no sprayed plants), amino acids at 300 ppm, silicon at 1 ml/L, seaweeds extract at
3 ml/L, amino acids + silicon, amino acids + seaweeds extract, silicon+ seaweeds extract, amino acids + silicon
+ seaweeds extract. The revealed results indicated that the use of compost at all levels led to a significant increase
in plant growth traits (plant height, branch number / plant and herb dry weight/ plant) and also sepals dry yield/
plant and /fed., as well as % anthocyanin. In addition, all levels of compost significantly augmented acidity %
except for the low one of compost (8 m³/ fed.) in the second season. The highest values of these traits were detected
by applying the high level of compost (24 m³/ fed.). It could be noticed. That foliar spray with stimulant substances
either single or together resulted a significant augment in these studied parameters, except for silicon treatment,
mostly and, also amino acids treatment concerning acidity % in the second season. The application of the triple
combined treatment (amino acids + silicon + seaweeds extract), followed, by the double combined one (amino
acids + seaweeds extract) gave the highs values of plant growth characteristics. In connection, the highest values
of sepals yield/ plant and fed., % acidity and anthocyanin % were given by foliar spray with the triple combined
treatment (amino acids + silicon + seaweeds extract). The data showed that all studied traits were significantly
affected by interaction treatments. Most combined treatments caused a significant increase in all examined
parameters. In most cases, the addition of compost at the high level (24 m³/ fed.) with foliar spray with the triple
combined treatment (amino acids + silicon + seaweeds extract), followed by the double combined one (amino
acids + seaweeds extract).